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Message-ID: <20230617182609.GA410998@sumitra.com>
Date: Sat, 17 Jun 2023 11:26:09 -0700
From: Sumitra Sharma <sumitraartsy@...il.com>
To: Thomas Hellström (Intel)
<thomas_os@...pmail.org>
Cc: Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>,
intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, Deepak R Varma <drv@...lo.com>,
Fabio <fmdefrancesco@...il.com>,
Thomas Hellstrom <thomas.hellstrom@...el.com>,
Ira Weiny <ira.weiny@...el.com>,
Matthew Auld <matthew.auld@...el.com>,
Sumitra Sharma <sumitraartsy@...il.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Call page_address() on page
acquired with GFP_KERNEL flag
On Wed, Jun 14, 2023 at 05:30:25PM +0200, Thomas Hellström (Intel) wrote:
>
> On 6/14/23 15:22, Tvrtko Ursulin wrote:
> >
> > On 14/06/2023 13:35, Sumitra Sharma wrote:
> > > Pages allocated with GFP_KERNEL cannot come from Highmem.
> > > That is why there is no need to call kmap() on them.
> >
> > Are you sure it is GFP_KERNEL backed and not tmpfs? I am not sure myself
> > so let me copy Matt and Thomas if they happen to know off hand.
>
Hello,
Yes it is true that the pages have not been acquired using the GFP_KERNEL.
I confused the allocation of the struct 'i915_vma_resource' tracking the
pages with the allocation of the pages themselves.
This was noted by my mentor Ira Weiny <ira.weiny@...el.com>.
> It looks to me these are shmem pages or TTM pages. Both could be highmem. So
> I think kmap is the correct choice here.
>
However, the kmap() will not be the correct choice here and kmap_local_page()
must be used instead. I have created a v2 patch for the same
https://lore.kernel.org/lkml/20230617180420.GA410966@sumitra.com/
Thank you for helping me.
Regards
Sumitra
> /Thomas
>
>
>
>
> >
> > Regards,
> >
> > Tvrtko
> >
> > > Therefore, don't call kmap() on the page coming from
> > > vma_res->bi.pages using for_each_sgt_page() in
> > > i915_vma_coredump_create().
> > >
> > > Use a plain page_address() to get the kernel address instead.
> > >
> > > Signed-off-by: Sumitra Sharma <sumitraartsy@...il.com>
> > > ---
> > > drivers/gpu/drm/i915/i915_gpu_error.c | 3 +--
> > > 1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c
> > > b/drivers/gpu/drm/i915/i915_gpu_error.c
> > > index f020c0086fbc..6f51cb4fc55c 100644
> > > --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> > > +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> > > @@ -1164,9 +1164,8 @@ i915_vma_coredump_create(const struct intel_gt
> > > *gt,
> > > drm_clflush_pages(&page, 1);
> > > - s = kmap(page);
> > > + s = page_address(page);
> > > ret = compress_page(compress, s, dst, false);
> > > - kunmap(page);
> > > drm_clflush_pages(&page, 1);
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